Wastegate valves on diesel engines

In a roundabout way ...

If the wastegate is leaking badly the turbocharger will not recover as much energy from the reduced exhaust flow. This means that charge air flow is also reduced and that reduces the power output at which smoke point is reached.

You don't say which engine model it is so it is impossible to go much further with the information available. Talk to a dealer or shop that works with those engines.

Thanks. Those engines have a boost control system that uses the waste gate to bleed off exhaust now the question is, is the wastegate actually leaking or is the boost control system malfunctioning?

Do you think the wastegate is leaking because boost is low?

I think it might be more productive to have a MAN tech look at the engine and determine if anything is out of spec before throwing parts at the engine or taking things apart.

Those are right (boost, air inlet temp) where they should be. Yes, MAN has had issues with the waste gates on your style diesel, but your motors are not experiencing that and it's not your issue. How many hours are currently on your engines? Have you had the valves adjusted, injectors and or nozzles checked, I think yours has nozzles, fuel injector pump checked? Usually on MAN's around 1000 hours the injector pump will make them smoke more and it's supposed to be check along with injectors or nozzles. Valve adjustment is supposed to be done at 800 hours. Have the aftercoolers ever been cleaned? That should be done every 1000 hours or sooner (MAN calls for 1000 hours or every 2 years, nobody ever does them every 2 years). What's your air inlet pressure? You should see less than 5? Dirty/restricted air filters will also cause smoking. Does yours have paper ones or washable? If washable and over 10 years old, and crushed looking, replace them.

All the above is precisely why you should have a MAN tech verify the engines are operating within tolerances. Unless you have a way to connect your engines to your router so a tech can access the data all anyone can do on the internet is point in a lot of different directions.

It is beginning to sound like nothing may be wrong. The amount of soot staining and its appearance, particularly after a new paint job, is highly subjective and it might be a case that the same amount of soot is just more visible. Just for the sake of discussion, if we are to assume your engines meet the EPA emissions standards for 2006 and are running at 50 percent power in test cell perfect conditions they may be exhausting about a half ounce of soot and other particulates every hour, probably considerably more in real life conditions. That is the nature of the beast and nothing other than exhaust post treatment can change that.

It might be worth testing the fuel for quality and sulfur content before calling in the pros. Have you loaded fuel in the Bahamas recently? If you did there is a good chance that it was not ULSD (regardless of what the bunker ticket says) and particulate emissions increase substantially with sulfur content.

What rpm's do the engines reach at WOT, if the boat is a little overpropped, it will cause them to run a little sootier than normal at cruise speed. But, I agree with Marmot that it might be time to call in a MAN tech with his laptop. Since you've done valve adjustment/aftercooler/air filters are clean/boost is where it should be. What's your fuel pressure when running at cruise? Man common rails normally run 70-86 psi fuel pressure. The only thing that comes to mind for me is fuel delivery (injectors or etc.) or slightly overpropped.

Providing you have the proper fuel pressure and not dirty fuel filters, it's really pointing to injectors. Everything else appears right. Do both motors smoke equally or is one smoking more than the other? Do you notice any weird sheen on the water coming out of the exhaust at idle at the dock? Any smoke on cold startup while it's warming up? Visually how bad is the smoke on a scale of 1-10?